Metallurgical apparatus



Dec. 25, 1945. c. J. WESTLING METALLURG I CAL AP PARATU S Filed June 4,. 1942 3 Sheets-Sheet 1 FIGJ,

INVENTOR. CARA Jflsru/va W TTORNEY.

Dec. 25, 1945.

C. J. WESTLING.

METALLURGI'CAL APPARATUS Filed June 4, 1942 :5 Shets-Sheet 2 I INVENTOR. CARL J M1574 //VG 2 I ATTORNEY.

Dec. 25, 1945. c. J. WESTLING 2,391,495

METALLURGICAL APPARATUS F iled Jun e 4, 1942 s Sheets-Sheet s INV EN TOR. 64/424 JWs-srz m/a Patented Dec. 25, 1945 Carl J. Westling, West Orange, N. J., Minerals and Metals Corporation,

assignor to New York.

N. Y., a corporation of Delaware Application June 4, 1942, Serial No. 445,721

8 Claims. (Cl. 259- 4) This invention relates to the beneflciation of finely divided metallic compounds or ores by reduction, roasting. or other metallurgicalproc-'- esses, and relates particularly to improvements in the apparatuses disclosed in my copending application Serial No. 422,930, filed December 15,

asmu n as in operations in which the reducing agent used contains a substantial ercentage of hydrogen, leakage of air from the shaft may con- 1941, and to improvements in multiple circular hearth furnaces.

Furnaces or roasters of the multiple hearth type are well known in the art. These furnaces include a number of circular arch refractory hearths built one above another in a suitable fur nace shaft. Ore is fedto the top hearth and is then rabbled toward the center where it drops to the hearth below, then rabbled toward the outer periphery of the hearth where it drops again to the next lower hearth, and so on down through the furnace.

The rabbling is accomplished by means of a plurality ,of arms provided with inclined plow blades which are mounted upon a common hollow central shaft that is rotated in any suitable way to advance the ore through the furnace shaft as described above.

stitute a serious explosion hazard.

An object of the present invention is to. overcome thedisadvantages of such multiple circular hearth furnaces as those described above and to provide an apparatus for more efficiently re- 1 ducing, roasting or otherwise treating ores or metallic compounds.

Another object of the invention is to combine the advantages of an efficient reducing furnace,

such as that described in application Serial No: 4

422,930 with the multiple circular hearth type of furnace to obtain a more, eflicient heat interchange between the gases coming up through the bottom of the furnace and the charge and toutilize gases for the pretreatment of. the charge.

. Reduction of the ore is accomplished in furg5 naces of this type by the flow of a reducing gas countercurrent to the direction of movement of the ore. The gases and furnaces of this type act on the charge by flowing over it on the ,hearths andby flowing through the charge as it drops from one hearth to the next lower hearth. The reaction of the gas with the charge in this type of furnace is relatively quite slow, especially when the object of the treatment is toreduce an ore to metal. The reason for this is that the major portion of the gases bypass the material and do not come in close contact with the material undergoing reduction. Moreover, the heat for reduction usually is obtained by burning the gas at the diflerent hearths with the result that the products of combustion mix with the reducing gases and diminish the reducing action thereof.

Another difllculty encountered when using this type of furnace for reducing ores is that, as the ore is changed gradually to ametallic state, it has a tendency to sinter and stick to the hearths and rabbles at the zones where there are concentrations of heat sumcient to soften .the metallized particles.

It is customary to cool the shafts and the rabble arms of such furnaces by passing air through the arms and the hollow shaft. This cooling operation-has the disadvantage that it removes a large amount of the heat, from the furnace and moreover may be a source of potential danger in- 66 j by isolating the gases in Another object ofthe invention is to overcome the danger of explosions in such furnaces and to provide a more efliclent cooling of the rotating shaft and the stirring or rabbling arms of such a multiple circular hearth furnace and at the same time to make use of the heat so absorbed from the mechanism to dry and heat'the freshly introduced ore.

-In general, furnaces and masters of the type embodying the present invention resemble the multiple circular hearth furnaces described above, in that they include the usual circular.

refractory hearths, the rabbling arms or stirrers and the central hollow shaft supporting such arms for rotation. In these older furnaces the flow. of material is radial alternately in or out from the center to the outside and vice versa. My device differs from prior devices, however, by the provision of a reducing hearth at the bottom of the shaft including a plurality of circular troughs through which the charge is caused to flow circumferentially, by directing reducing gases upwardly through the bottom of the troughs, thereby causing a state of fluidity in the charge and assuring intimate contact between the gases and the charge. The partially spent reducing gases then flow countercurrent to the charge on the hearths to preheat: and

drive off the moisture in the charge. Also, inasmuch as the reducing gases contain acertain amount of reducing agents, a partial reduction of the ore is obtained as the ore is brough p to the desired temperature. v r

' In the event'that the ore used requires roast;- ing to drive off sulfur'or carbon dioxide, uns at?- tion may also be accomplished in my furnace the. roasting section from panying drawings. in which:

the gases in other-hearths of the furnace. With an ore of this type. a further advantage is gained by conserving the heat in the ore from the roasting operation since it passes immediately down to the reducing hearths without cooling or rehandling.

- In furnaces of the type embodying the present invention the central shaft for supporting the rabbling arms may be cooled by means of washed spent reducing gases. thereby. minimizing the danger of explosions in the shaft. The furnace is so arranged that when the cooling gases reach the level of the top hearth, they are discharged over it from the shaft and arms and thence pass into an additional top deck in the furnace inthe form of a heat exchanger through which the gases may flow to give up their heat to the raw ore fed to the top of this deck, therebydrying it and placing it in condition for further treatment. This gas, inasmuch as it is isolated from the other reducing gases, preferably by means of gas lock, may then be sent through a washer, cooled and recirculated through the shaft to cool the shaft and to dry additional quantitles of ore. The use of recycled gas for cooling purposes holds the heat loss at a minimum by transferring to the cold ore the maximum .amount of sensible heat picked up in the shaft and rabbling arms.

For a better understanding of the present invention, reference may be had to the accom- Flg. 1 is a view in vertical section of a typical form of a furnace or roaster embodying the present' invention:

. Fig. 2 is a view in section taken on line 2-2 of Fig. 1:

Fig. 3 is a view in section taken on line 3-3 of Fig. 1;

Fig. 4 is a view in section taken on line 4--4 of Fig. 1;

Fig. 5 is a view in section taken on line 5-5 of Fig. 1, and

Fig. 6 is a view in section taken on line 6-6 of Fig. l.

The form of the invention chosen for purposes of illustration may consist of a cylindrical re-- fractory furnace shaft I9, which is mounted on suitable standards II and is provided with a plurality of substantially circular refractory hearths ceived on the deck plate I5a. As shown in Fig.

2, the space between the plates I51: and lib may be formed into a spiral gas passageway I9 by means. of the outer casing of the furnace and, a spirally arranged plate lid. The inner end of this passageway communicates through an opening lie with the space in the furnace shaft between the upper refractory hearth I3 and the deck IS. The passageway I9 is provided with an outlet I1 opening to the exterior of the furnace for a purpose which will be described hereinafter.

The bottom of the furnace shaft I9 is. closed by means of a refractory hearth I8 which is provided in its upper surface with a pair of generally v-shaped, annular troughs I9 and 29. As shown in Fig. 3, an inclined passage 2I of generally V- shaped cross-section connects the troughs I9 and 29 so that the chargev which is received in the trough I9 may be transferred outwardly tothe trough 29. v

Partially reduced and/or preheated ore isadvanced around these troughs by means of a gasy it a fluidity similar to water.

eous current in a manner similar to that disclosed .ln application Serial No; 422,930 referred to above. As described in application Serial No. 422,930, the gas passing -upwardly through the body of ore acts to suspend the ore and impart to The flow of the finely divided ore is accomplished by maintain ing a greater depth of ore at the feed end of the hearth than at the discharge end,'thereby caus- 1 ing the ore to flow like water under a pressure head. The ,bottom'ends ofthe troughs at the apex thereof are provided with circumferential slots I9a and 29a which communicate with gas supply manifolds 22 and 23. respectively.

As best shown in Fig. 4, the manifold 23 is of annular formation and includes a laterally extending port 23a through which the heated reducing 'gas is delivered into the channel 29 from an exterior source, not shown.

. The manifold 22 is of semi-circular shape, concentric with the manifold 29 and is provided with an inlet port 22a for the heated reducing gas. The hearth I9 is further provided with a plurality of radially extending passages 24 communicating with the passage 22 and radially extending passages 25 communicating with the manifold .28.

These passages communicate, in turn, with upwardly extending passages 26 and 21, through which the reducinggas is delivered into the bottom slots I 9a and 29a of the troughs I9 and 29. As shown, particularly in Figs. 5 and 6, the slots I9a and 29a are not entirely open but reinforced at intervals with vertically extending refractory members 29 having generally yramidal top portions 29a terminating at the bottoms of the troughs I9 and 29. These members 29 contain ducts horizontally communicating with the passages 29 or 21 to deliver the gases into the slots I91: and 29a of the troughs I9 and 29. As shown in Figs. 1 and 5, the ducts 28b in the members 28 may be provided with manually adiustable slide valves 29a which are adjustable from the exterior of the shaft to control the rate of flow of gas upwardly through the troughs and thereby control the reduction rate and the rate of flow of the charge.

The provision of two separate manifolds 22 and 23 permits a washed recycled gas to be introduced into the inner trough I9 and fresh reducing gas to be introduced into the trough 29. As a result, a marked reduction in the volume or the fresh reducing gas can be made and a more economical treatment of the ore results.

In order to prevent sticking of the ore in the troughs I9 and 29 and to assure a loose formation of the particles of the charge so that free passage of the gas therethrough and intimate contact between the reducing gases and the charge are obtained, stirrers may be provided. As illustrated inFig. 1, the stirrers 39 may be of generally triangular outline and formed of a vertically extending rod 99a having a plurality of cross pieces 99b thereon. These stirrers 39 are mounted on arms 9I, which are, in turn, supported on a hollow cylindrical-shaft 92 that is rotatably mounted concentrically with the furmee shaft. As illustrated in Fig. 1, the shaft 32 may be supported at its lower end by means of a bearing SI and is driven by means of a suitable in: operation. The advantage of keeping this shaft cooling gas separate fromthe spent reducing gases passing out of the outlet 41 is that this cooling gas will not pick up. as much dust since this gas purposely will not contain enough heat to dry the ore to a dusty state and this gas therefore does not require extensive cleaning before being recycled.

II and the deck IS. The rabble blades 39 on the arms 30 are so inclined that the ore which is fed into the hopper It at the top of the furnace shaft and onto the shelf ll therein, is fed inwardly along the deck IE to the aperture 42 adjacent the shaft 32 through which it falls to the shelf 43 above the next adjacent hearth l3, ismoved outwardly by the blades 39 to the periphery of the hearth to fall onto the next adjacent hearth, finally falling to the hearth l8 adjacent its center zone. The stirring blades 39 on the arms 3| then move the charge slowly outwardly into the trough l9, and create a pressure head on the ore by producing a greater depth of ore in the trough IS. The ore suspended in a state resembling fluidity by the gases flows around the trou h l9 toward the transverse or inclined trough 2|,

1 shown in Fig. 3. The charge is then transferred.

through the trough 2| by means of the flow of the gases and the pressure head into the trough where it is advanced by and subjected to further action of the treating gases as it passes around this trough to the discharge opening 46.

Control of the flow of the charge through the troughs I 9 and 20 may be obtained by varying the supply of gas delivered to various portions of the troughs by means of the valvesfsa. Thus, if the gas is shut oil from any one section of the trough It, the chargeat this zone will be quiescent and will form a dam preventing the flow of the charge beyond this dam. Nevertheless, the stirrers can pass through the quiescent portion of the charge without advancing it appreciably. Advantage may be taken of this flow or lack of now to direct the transfer of ore from one trough Is to the other trough 20 and also to control the circumferential flow in the troughs sothat it will be continuous in one direction toward the reduced product exit port.

Additional heat for a reducing operation can be obtained, if desired, by burning some of the reducing gases at various zonesabove the hearths. Thus, effective control of the heating conditions within the furnace can be obtained. The par- 7 tially or completely spent reducing gases may be drawn off through the gas outlet 41 between the hearths I 2 and I3 so-that these gases do not affect the ore on the deck I! or the hearth it.

In order to eifect' cooling of the shaft 32 and arms if and 38 and drying of the ore on the deck l5, washed spent reducing gases may be introduced into the shaft 32 through the manifold 48 at the lower end of the shaft 32. The gas travels upwardly through the shaft 32 and arms II and 38 absorbing heat therefrom. This heated gas' may then be discharged through the port 32a be- 7 tween the hearth l3 and the deck I! and then passes through the gas port I60 into the spiral passage l5, dissipating its heat through the steel plates Ila and llb and drying the ore traversing the deck IS. The gas may then be withdrawn through the outlet port If, rewashed and recycled through the shaft 32 for another cooling and dry- From the preceding description of a 'typical form of apparatus embodying the present invention, it will be clear that I have provided an emcient apparatus for reducing or otherwise treating ores or other materials at relatively low temperature and in which high efliciency is obtained, because of the intimate contact of the gases with the material beingtreated. Moreover, there is less waste of gas and of the heat of thegas because of the efllcient heat interchange in the various stages 'of the apparatus. The multiple rabble hearth section of the furnace is used primarily as an efficient heat exchanger between the downflowing ore and the hot gases coming up from the trough-type reducing section at the bottom.

However, some reduction will'take place on the upper hearths if the conditions are favorable toward such reduction. The extent of reduction is, of course, dependent upon temperature conditions, the equilibrium between the oxide and the gases and the time required for the oxide to traverse the upper sections of the furnace. The time is further dependent upon the rate at which the reduction of the ore can be completed in the troughs l9 and 20.

It will be understood that the device is susceptible to considerable modification in its details of construction and that the number and size of the hearths, the number and size of annular reducing troughs, the details of the rabbles, and the havingat least one curved trough therein extending around the hearth for receiving said material and having a perforate bottom, and means for supplying as under pressure through the perforate bottom of said trough to render said ma.-

terial fluent so that it flows along said trough and to bring said gas into intimate contact with said material. v

2. An apparatus for treating. a finely divided solid material with a gas comprisinga furnace shaft, a substantially circular hearth therein having a plurality of substantially annular troughs therein for receiving said material, means for supplying gas under pressure through the bottom of said troughs to render said material fluent so that it flows along said troughs and to bring said gas into intimate contact with said material, and at least one passageway connecting said troughs for transferring said material from one trough to another.

3. An apparatus for treating a finely divided material with gases, comprising a furnace shaft, at least one substantially circular hearth therein having a plurality of downwardly tapering openbottom annular troughs therein, means for introducing a gas through the bottoms of said troughs to buoy the material upwardly so that the'matetreating a finely divided solid material with a gas comprising a furnace shaft, a substarrtialhl circular hearth therein rial flows around the troughs, and at least one downwardly tapered open-bottom trough com municating with the adjacent first-mentioned troughs for transferring the material from one of said first-mentioned troughs to another,-

l. An apparatus for treating a finely divided solid material with a gas, comprising a furnace shaft, at least one substantially circular hearth in said shaft, having a plurality of annular troughs concentric therewith and each having a perforate bottom, means for ieeding said material to substantially the center zone of said hearth, means for advancing said materiel out wardly into the innermost trough, means for directin a gas upwardly through the perforate bottoms of said troughs to render the material fluent so that it flows around said troughs, and means for transferring said material from the innermost trough outwardly into the next adjacent trough.

5. An apparatus for treating a finely divided solid material with a gas, comprising a furnace shaft, at least one substantially circular hearth in said shaft, having a plurality of annular troughs concentric therewith and each having a perforate bottom, means for feeding said material to substantially the center zone of said hearth, means for advancing said material outwardly into the innermost trough, means for directing a gas upwardly through the perforate bottoms of said troughs to render the material fluent so that it advances around said troughs, means for transferring said material from the innermost trough outwardly into the next adjacent-trough, and means rotatable about an axis concentric with said troughs for agitating the material therein.

6. An apparatus for treating a finely divided solid material with a gas comprising a furnace shaft, a substantially circular hearth therein having at least one substantially annular trough therein for receiving said material and having a perforate bottom, means for supplying gas under pressure through the perforate bottom of said assures trough to render said material fluent so that it flows along the trough and to bring said gas into intimate contact with said material, and means for selectively controlling the flow of gas into different portions of said trough to control the rate at which the material can advance along said trough.

7. In a furnace, the combination of a iurnace shaft, a plurality of vertically spaced substantially circular hearths in said shaft, having apertures therein for passage of material downwardly from one hearth to another, means for advancing said material along said hearths toward said openings, another hearth in the bottom of said shaft having at least one substantially annular trough therein ior receiving material delivered from the hearths next above, said trough being substantially V-shaped in cross-section an new ing a slot at its bottom, and means for delivering a heated gas through said slot to render said nae terial fluent so that it flows alongsaiol trough, said gas thereafter flowing upwardly through said furnace shaft countercurrent to the movement of said material.

8. In a furnace, the combination of a furnace shaft, a plurality of vertically spaced substantially circular hearths in said shaft, having apertures therein for passage of material downwardly from one hearth to another, means for advancing said material along said hearths toward said openings, another hearth in the bottom of said shaft having a plurality of substantially annular troughs therein for receiving said material, said troughs being substantially V-shaped in crosssection and having narrow annular slots at their bottoms, an inclined v-shaped trough having a slot in its bottom connecting adjacent annular troughs, and means for delivering a heated gas through said slot to render said material fluent so that it flows along said troughsaid gas thereafter flowing upwardly through said furnace shaft countercurrent to the movement of said material.

CARL J. WESTLENG. 

